Possible regression in certain SMP configuration

Description

I have an Intel i3 with two physical cores and HT. The host is 64bit Debian Sid. I have a WinXP VM with 3 virtual CPUs, VT-x and nested paging. With 3.2.8, if I recall correctly, there was no problems. With 3.2.10 the VM constantly eats CPU, shown on the host as continuous 40..60% usage, and all operations in the guest are very slow and laggy (the guest CPU "usage" is distributed between several processes with csrss.exe usually on the top, DPCs in Process Explorer sometimes use up to 20%). If I lower the guest CPU count to 2 or 1, the problems disappear. The same is with Win7 64bit guest.

I've downgraded VirtualBox to 3.2.8 to check whether it is a regression and VMs worked without lags. The I upgraded back to 3.2.10 and there is still no lags, but I'm pretty sure they existed.